6. Abstract Objects Layer

The functions in this chapter interact with Python objects regardless
of their type, or with wide classes of object types (e.g. all
numerical types, or all sequence types). When used on object types
for which they do not apply, they will raise a Python exception.

It is not possible to use these functions on objects that are not properly
initialized, such as a list object that has been created by
PyList_New(), but whose items have not been set to some
non-NULL value yet.